Growing Degree Day, Your Safe-to-spray Number

The cold winter we’ve experienced in the south has its pros and cons. Winter-kill is a possibility, but for the first time in years I'm comfortable spraying Ronstar on non-overseeded bermuda. That doesn't mean, however, that timing isn't still of importance.

Patrick McCullough at the University of Georgia has come up with a Growing Degree Day (GDD) model that shows the cutoff to insure safety is 100 GDD or less. Syngenta has an easy to use GDD calculator on their website which can be found here. Unless you’re in the upper part of the transition zone time is quickly running out to spray!

If you choose to use granular Ronstar this year, be sure to use a mini prill (<200 SGN) and as high a spread as possible for optimum coverage. Dr. Mudge from Bayer has recommendations here.

If you’d like to kill two birds with one stone have your Ronstar sparged onto a blend containing POLYON controlled-release fertilizer. The example below is a 20-0-20 Mini granular fertilizer with 90% Polyon 41 and a 0.67% Ronstar sparged onto it. This provides 2lbs of N/M and and 2.91lbs AI of Ronstar. It also will provide 21 weeks of greening! That’s enough to keep your turf green through the 4th of July!